Radar target simulator



5 Sheets-Sheet 1 J. J. PASTORIZA ETAL RADAR TARGET SIMULATOR Dec. 24, 1963 Filed Deo. 5, 1961 Dec. 24, 1963 3,115,535

J. J. PASTORIZA ETAL RADAR TARGET SIMULATOR Filed Deo. 5, 1961 5 Sheets-Sheet 2 A QV-H" @h y Dec. 24, 1963 .1.J. PAsToRlzA ETAL RADAR TARGET SIMULATOR 5 Sheets-Sheet 3 Filed Dec. 5, 1961 Dec- 24, 1963 .1. J. PAsToRlzA ETAL 3,115,535

RADAR TARGET SIMULATOR 5 Sheets-Sheet 4 Filed Deo. 5, 1961 ...AAA l vvvvv A; vvvvv H S@ Qwm Dec. 24, 1963 J. J. PAsToRlzA ETAI. 3,315,535

RADAR TARGET SIMULATOR Filed Deo. 5, 1961 5 Sheets-Sheet 5 :2" S Ef-11i INVENTORS United tates l llili Patented Bec. Zeit, E563 3,ll5,535 RADAR EMULATR .lames 5. Pastoriza, Boston, William F. Ring, Lexington,

and Frederick F. Slack, Stoneham, lVlass., assignors to the United States or America as represented by the Secretary of the Air lorce Filed Dec. 5, wel, Ser. No. 157,283

3 Claims. (Cl. 35i-10.@

(Granted under 'lfitie 3S, US. @ode (H52), sec. 266) 'fi e invention described herein may be manufactured and used `by or for the United States Government for governmental purposes without payment to us of any royalty thereon.

This invention relates to a signal generator and more particularly to a generator wherein the signals generated have the gc eral characteristics or" the radar signals returned by a target aircraft in ilight.

The signal generator of the present invention can be also referred to as a radar target simulator. The target simulator' generates a video signal which has the general characteristics of the radar return signals representative of an aircraft in flight. The simulated radar signals are displayed on a plan position indicator (lJPl) and are then utilized ior raining purposes.

An object of the present invention is to provide a target simulator wherein the simulated signals have the general characteristics of the radar return signals of an aircraft in night.

Another object or the present invention is to provide a target simulator in which simulated signals are generated for visual presentation upon the `tace of a plan position indicator.

Still another object of the present invention is to provide a target simulator in which the simulated signals are representative of radar return signals orP an airborne object as to heading, velocity, bcarnwidth and x and y coordinate positions.

These and other obiects and advantages of this invention, which will be in part obvious and in part pointed out hereinafter, are obtained by the means described in the following specication, and may be more readily understood by reference to the accompanying drawings, showing one of the various possible embodiments of this invention, in which:

FiGUiE l is a bloei: diagram of the preferred enibodiment of the present invention;

Fl vURE 2 is a block diagram orF the :t and y generator shown in FGURE l;

FGURE 3 is a diagram of the x channel, FlGURE l, partly in schematic and partly in bloc-k;

FGURE 4 is a diagram of the y channel of FGURE l `artly in schematic and partly in block form;

FEGURE 5 is the schematic diagram of components i5, lf3, i7, and i@ or FGURE l; and

FIGURES 6 and 7 illustrate various pertinent Waveforms of the preferred embodiment of the present invention.

Now referring in detail to FlGURE l, there is shown :c sweep generator and y sweep generator 2li, each of which provides a sawtooth voltage which continuously varies in amplitude from a maximum positive value to an identical maximum negative value. The x and y sawtooth wavnorms are displaced from each other by 90. These types or" sawtooth waveforms are conventional in an electronic PPI scope, and is explained in detail hereinafter by referring to FGURE 2 in which the x and y components are formed for an electronic PP-l scope. he x and y components are formed by passing a sawtooth waveform Afrom timer 59 through a sine, cosine resolver S .connected to radar scanner 52, thereby producing two components of the same waveform but proportional respectively to the sine and cosine of the orientation angle of the resolver. The x component may be passed through amplicr 53 and the y component through amplifier 54, This is a conventional manner of generating x and y sawtooth waveforms for utilization in an electronic plan position indicator, and is shown and described on pages 26 through 28 of the Radiation Laboratory Series, vol. 22, entitled Cathode Ray Displays, published in 1948 by McGraw-Hill Book Company, Inc. lt is to be noted that the above described generators of x and y sawtooth waveforms is commonly referred to as the Resolved Time Base Method of PPl synthesis and is more completely shown and described at pages 534-544 of vol. 1 of Radiation Laboratory Series entitled `Radar System Engineering, published in 1947 by McGraw-Hill Company, lne.

Now referring again to FGURE 1, the x sawtooth signal from generator l@ is fed to x comparator il. which simultaneously receives a DC. signal from x path generator i2. The x path generator produces a direct current signal which is representative of the position heading and velocity of an air-craft in light. Whenever coincidence in amplitude occurs in comparator lll, then ampliiication results therein and an output signal is provided therefrom to diode matrix i3. The y channel comprising y sweep `generator 2i?, y path generator 22, y comparator 2t and diode matrix 23 operates in the identical fashion as the x channel. X diode matrix i3 is interconnected with y diode matrix 23 and a pulse is produced at point lift only at the instant that x DE. position voltage is coincident with the x sweep voltage and the y DE. position voltage is coincident with the y sweep voltage. The pulses at point i4 are fed through video pulse Shaper and amplifier t5 to diierentiator lo. The diierentiated signal is applied to normally non-.conducting multivibrator l. The first positive portion of the differentiated signal triggers multivibrator 1S and thereupon multivibrator if@ produces a pulse output with a preselected width which is applied to gate on amplier 17. During the period ampliiier 17 is gated on, only positive portions of the `differentiated signal are amplilied and pass to cathode follower 19. The preselected width or" the output pulse from multivibrator t8 permits a simulation of radar beamwidth. The output pulses from cathode follower 7.9 are video in nature and are applied to the video signal input of electronic PPI scope for visual presentation upon the face thereof.

Now referring to FGURE 3, for a more detailed description of the mode of operation of the x channel structure shown in FlGURE l, x path generator is comprised of vacuum tubes Btl and 3l. "the y path generator is comprised of vacuum tubes l5@ and lSl, FIG. 4. Since the x and y channels are identical, only the x channel is described. The x path generator is an RC. integrator which produces an x position direct current voltage. esistor 32 is connected in series with potentiometer 33 and resistor 3d. At point 35 is connected a positive voltage source and at point 36, a nevative voltage source. The movable arm of potentiometer 33 is connected by Way of double pole-double throw position release switch 37 to the positive side of battery and also to the grid electrode oi"- vacuum tube Sil. The negative side of battery 33 is connected to capacitor 39, two ganged speed range selector switch 44E and to dual, sA ced potentiometer 47 by way of double pole-single throw velocity release switch 46. The movable arm of potentiometer 47' is connected to the movable arm of dual-sine leading potentiometer 49 by way of resistor One end of potentiometer 49 is connected to the cathode electrode of tube 3l?, the other end is connected by way of fuse 59 to the movable arm of potentiometer 5l. It is to be noted that each of potentiometers 33, 57, and 5l has movable` arms and the direction of theirr clockwise travel is represented by the legend CIJ. as shown in FiGURE 3. 'he aforementioned CW. legend is also associated with and identical in meaning for potentiometers 53, 67, and 7i of FEGURE 4. One end of potentiometer Sil is connected to the anode of tube 3l. The grid of tube 33t is connected to 150i volt negative source and the cathode by way of resistor 52 to a 300 volt source of voltage. The anode of tube 3@ is connected to a I+360 volt source of voltage. Tube 3i serves as a constant current tube which produces a constant voltage across heading potentiometer Linearity is provided through the bootstrap cathode follower 3i?. in the operation of the lcircuit comprised of tubes Sil and 3d, the movable arm of potentiometer 33 is set to any desired point and switch 37 is .closed momentarily. The adjustment of movable arm of potentiometer 33 permits the selection of DE. voltage at the grid of tube 3@ and this preselected voltage is representative of the initial x position of the simulated target. `he adjustment at potentiometer :'33 of FIG. 4 operates in the same manner to select the initial y position. Capacitor 39 receives a preselected charge by way of battery B and the rate of charge is determined by the setting of potentiometer d'7. The direction of the charge is selected by potentiometer .9. It is thus seen that a DC. voltage is then impressed upon the grid of tube 3i). The initial value of the DC. voltage is determined by the initial charge on `Capacitor 39 and is representative of the initial position of an aircraft target. The rate of charge as determined by potentiometer 47, is representative of the speed of the target and the setting of poentiometer i9 is representative of the heading thereof. There is also another adjustment provided which is comprised of switch 4@ wherein capacitor 39 may be connected to ground alone or have paralleled therewith either capacitor 44 or d5. This provides a speed range selection. It is thus seen that there is available a D C. voltage which is representative of a tar-get having position, speed, and heading. It is to be noted that the x path generator is identical to the y path generator with the additional feature that position release switch 37 and 57 is comprised of a double pole-double throw switch; velocity switch 46 and 65 is comprised of a double pole-single throw switch; selector switch dit is ganged to selector switch 6tlg speed potentiometer 47 is one part of a dual potentiometer with speed potentiometer 67 being the other portion thereof; and heading potentiometer d@ is a portion 0f a dual system with heading potentiometer 69.

The x comparator is comprised of two differential ampliers. The first differential amplifier is comprised of tubes Si), 81 and 82 and the second differential amplilier is comprised of tubes 83, S4 and 55. rThe varying DC. voltage representative of x target position, speed and heading is available at the cathode of tube 3i? and is applied to the grid of tube 8G'. Simultaneously therewith, a varying sawtooth waveform as illustrated as waveform n, of FIGURE 6 is applied to the grid of tube 3l by way of x sawtooth generator llt). Whenever a coincidence in amplitude occurs between aforesaid two input signals, amplification results and the anode of tube S0 has an output signal as illustrated as waveform b in FIGURE 6 and the anode of tube Sl has an output signal shown as waveform c of FIGURE 6. The output signal from tube Si) is applied to the grid of tube Se and that of tube Si to the grid of tube S3. The output signal of the anode of tube d3 is superimposed for illustration purposes on the output signal of the anode of tube lSd and is shown as waveform d of FIGURE 6.

A diode matrix is provided comprised of diodes 86 and 87 wherein the anodes thereof are interconnected. The output signal of tube S3 is applied to the cathode of diode Se and the output signal of tube is appliedto the cathode of diode 87. The output signal is provided by way of the aforesaid interconnected anodcs and is shown as waveform e of FIGURE 6. It is to be noted that the y channel comparator operates in the identical manner and that the anodes of diode matrix of the x comparator is interconnected with the anodes of the diode matrix of the y comparator. The purpose of the diode output matrices is to produce a range pulse only at the instant that the x DC. position voltage is coincident with the x sweep voltage and the y DC. voltage is coincident with the y sweep voltage. This output pulse is available at point 98 and is illustrated as waveform f of FGURE 6. This pulse at that instant is representative of a return radar pulse of an airborne object in liight.

New referring to FiGUiE 5, the output pulse from point 93 is applied to pulse Shaper and video amplifier which is comprised of tubes @9 162 and there is available at the grid of tube 31132 a pulse illustrated in FEC- UEE 6 as waveform g. rifube i162 and transformer 163 serve as a differentiator and at points title and 1%55 there is provided an output signal as illustrated as waveform /z of FIGURE 6. The signal from point lil/tis applied to the grid of amplifiertube lila and the output signal therefrom is applied to multivibrator comprised of tubes ll and ldd. The positive portion of the diferentiated and amplied signal (as shown as waveform i of FIG- URE 7) causes the multivibrator to provide a negative output pulse at the anode of tube Hi8. The width of the output pulse is determined by the setting of beam- Width potentiometer lil-9. The negative output pulse is illustrated as waveform j of FIGURE 7. This beamwidth output pulse is applied to the grid of tube M0. ri`ube il@ is normally conductive and because of the operating potentials applied thereto the positive portions of the differentiated signals cannot be applied to the lgrid of tube lll. When the negative pulse is applied to the grid of tube 11u, amplification of the positive portions of the diiferentiated signals Ifrom point 105 occurs and the signal input at the grid of tube 111 is illustrated as waveform k of FIGURE 7. vIt is seen that effectively tube M0 is a gated amplifier and provides a pulse output during the period a negative pulse is applied to the grid thereof. Thus, the number of pulses that is amplihed is representative of the beamwidth, and the beamwidth simulation is varied by potentiometer N9. The pulse output is in the form of video and is available from the interconnected Icathodes of tubes lil and 112. The lvideo pulse output is applied to the conventional Video input terminal of an electronic PPI scope such as PPI scope 25 and the pulses appear on the face of the PPI scope for visual presentation. There is thus provided a target simulator which can provide video signais for visual Idisplay on the face of a PPI scope in which the simulated signals have all the general characteristics of the return radar signals provided by an airborne object in flight. These aforementioned characteristics include initial position of the airborne object, its heading and speed, also the beamwidth of the radar that is looking at the airborne object.

What is claimed is:

1. A target simulator generating signals having the general characteristics of the radar return signals of an airborne object in flight comprising means to generate x and y sawtooth waveforms, each of said waveforms Varying continuously from a maximum positive value to the identical maximum negative value, said y sawtooth Waveform being displaced by from said x sawtooth waveform, means to generate x and y coordinate direct current signals, each of said signals being representative of the initial position, heading and speed of an airborne object in liight, lirst comparison means to compare the amplitude of said x D.C. voltage to the amplitude of said x sawtooth voltage, second comparison means to compare the amplitude of said y DC. voltage to the amplitude of said y sawtoot`i voltage, diode means interconnecting said first and second comparison means and operating to pass a pulse only at the instant that x D.C. position voltage coincides with said x sawtooth waveform voltage and the y D.C. position voltage coincides Wit'n the y sawtootli waveform voltage, a normally non-conducting multivibrator receiving and actuated by said passed pulse and operating to provide an output pulse therefrom of preselected Width to simulate radar beamwidth, an amplifier gated on for the period of said multivibrator output pulse and amplifying said passed pulses during said gated on period, and means to display on the face of a plan position indicator said passed pulses, the number of said passed pulses being representative of said radar beamwidth.

2. A target simulator generating signals having the general characteristics of the radar return signals of an airborne object in flight comprising means to generate sawtooth waveforms representative of the x coordinates of said airborne object in Hight, means to generate sawtooth waveforms representative of the y coordinates of said airborne object in flight, means to generate a direct current voltage representative of said x coordinate position, heading and speed of said airborne object in flight, means to generate a direct current voltage representative of said y coordinate position of said airborne object in flight, first means to compare the amplitude of said x direct current voltages to the amplitude of said x sawtooth waveforms, second means to compare the amplitude of said y direct current voltages to the amplitude of said y sawtooth waveforms, diode means interconnecting said first and second comparison means and operating to pass a pulse only at the instant the x direct current position voltage coincides with the x sawtooth Waveform voltage and the y direct current voltage coincides with the y sawtooth waveform voltage, and means to display visually on the face of a plan position indicator a preselected number of said passed pulses.

3. A target simulator as described in claim 2 wherein means to visually display a preselected number of said passed pulses includes a normally non-conducting multivibrator receiving and being actuated by said passed pulse to produce an output pulse therefrom of a preselected Width to simulate radar beamwidth, an amplifier gated on for the period of said multivibrator output pulse and amplifying said passed pulses during said gated on period, the number of said passed pulses being representative of said radar beamwidth.

Hales Apr. 13, 1954 Colker Sept. 6, 196() 

2. A TARGET SIMULATOR GENERATING SIGNALS HAVING THE GENERAL CHARACTERISTICS OF THE RADAR RETURN SIGNALS OF AN AIRBORNE OBJECT IN FLIGHT COMPRISING MEANS TO GENERATE SAWTOOTH WAVEFORMS REPRESENTATIVE OF THE X COORDINATES OF SAID AIRBORNE OBJECT IN FLIGHT, MEANS TO GENERATE SAWTOOTH WAVEFORMS REPRESENTATIVE OF THE Y COORDINATES OF SAID AIRBORNE OBJECT IN FLIGHT, MEANS TO GENERATE A DIRECT CURRENT VOLTAGE REPRESENTATIVE OF SAID X COORDINATE POSITION, HEADING AND SPEED OF SAID AIRBORNE OBJECT IN FLIGHT, MEANS TO GENERATE A DIRECT CURRENT VOLTAGE REPRESENTATIVE OF SAID Y COORDINATE POSITION OF SAID AIRBORNE OBJECT IN FLIGHT, FIRST MEANS TO COMPARE THE AMPLITUDE OF SAID X DIRECT CURRENT VOLTAGES TO THE AMPLITUDE OF SAID X SAWTOOTH WAVEFORMS, SECOND MEANS TO COMPARE THE AMPLITUDE OF SAID Y DIRECT CURRENT VOLTAGES TO THE AMPLITUDE OF SAID Y SAWTOOTH WAVEFORMS, DIODE MEANS INTERCONNECTING SAID FIRST AND SECOND COMPARISON MEANS AND OPERATING TO PASS A PULSE ONLY AT THE INSTANT THE X DIRECT CURRENT POSITION VOLTAGE COINCIDES WITH THE X SAWTOOTH WAVEFORM VOLTAGE AND THE Y DIRECT CURRENT VOLTAGE COINCIDES WITH THE Y SAWTOOTH WAVEFORM VOLTAGE, AND MEANS TO DISPLAY VISUALLY ON THE FACE OF A PLAN POSITION INDICATOR A PRESELECTED NUMBER OF SAID PASSED PULSES. 